fix: use more robust output cmd

cli/server/add.go

@@ -136,7 +136,11 @@ func newLocalServer(c *cli.Context, domainName string) error {
 	}
 
 	if provision {
-		if _, err := exec.LookPath("docker"); err != nil {
+		out, err := exec.Command("which", "docker").Output()
+		if err != nil {
+			return err
+		}
+		if string(out) == "" {
 			if err := installDockerLocal(c); err != nil {
 				return err
 			}